Citric Acid Cycle | MyPaperHub


Citric acid cycle, which is also referred Krebs cycle or tricarboxylic cycle, is a sequence of chemical reactions that are employed by aerobic creatures to produce stored energy, via the process of oxidation of acetyl- CoA into adenosine triphosphate (ATP) and carbon dioxide. The acetyl- Co A comes from fats, proteins and carbohydrates. Numerous citric acid cycle’s components and reactions were launched in the 1930s by a researcher known as Szent- Gyorgyi Albert. In 1937, Albert was rewarded the Nobel Prize in Medicine for discovering fumaric acid, which is the main element of the cycle. The Krebs cycle itself was discovered by William Arthur Johnson and Hans Adolf Krebs in 1937. Hans Adolf Krebs was awarded the Nobel Prize for Medicine or Physiology in 1953 (Ward, n,d ) Thus, the report will comprehensively talk about the functioning of the citric acid cycle. In this case, it will cover the steps of the cycle, processes and reactions. The report will also thoroughly explain the importance of the cycle. For instance, it acts as the central pathway of cellular respiration. Besides, the application of the cycle will also be incorporated in the discussion.

Importance of the topic

The topic is essential because it enables readers understand that the citric acid cycle has two other different names, i.e., Krebs cycle and tricarboxylic acid cycle. More so, enables readers clearly understand that the cycle is the fundamental cellular respiration driver. In this case, it acts as a common path for the oxidation of lipids, proteins and carbohydrates. The acetyl CoA, which emanate from the metabolism of fatty acids, glucose and amino acids, undergoes a series of reaction to generate energy. The CoA obtains a large amount of its energy in the form of FADH2, NADH and ATP molecules. The NADH and the FADH2 which act as the electron carriers will move their electrons into the chain of electron transport. Through the oxidation of phosphoryl, the electrons will produce ATP, essential for production of cellular energy. For instance, the ATP molecule will generate energy essential for muscle contraction (Chabra, 2017).  

The cycle not only acts as a pathway for oxidation of carbon units, it also acts as a major path for inter-conversion of metabolites that come from deamination and transamination of amino acids. It also provides the substrates for gluconeogenesis, and biosynthesis for haem and nucleotide. The citric acid cycle is Amphibolic because it plays a vital role in both synthetic and oxidative processes. Besides, the cycle acts as the entry for nutrients. In this case, the nutrients can enter as intermediaries of the cycle or as Acetyl CoA. Carbohydrates get in as acetyl Co A. The fatty acids enters as Succinyl Co A or as acetyl Co A. The amino acids penetrates at various points on the citric acid cycle for complete synthesis or oxidation of biological compounds depending on the needs of the cell (Chabra, 2017).                                

How the citric acid cycle functions

The citric acid cycle, which is also known as the tricarboxylic acid cycle or Krebs cycle, is a sequence of chemical reactions within a cell, whereby the food molecules are broken down into water, carbon dioxide and energy. Besides, the cycle produces NADH and FADH2, which are utilized in the transportation of electrons.  Most metabolic processes utilize the cycle’s intermediaries in their pathways.  In eukaryotic cells, the cycle takes place within the matrix of the mitochondria.  The citric acid cycle entails a chain of eight reactions, and utilizes a tiny molecule known as oxaloacetate, which acts as a catalyst. The reactions of the cycle can be divided into two varying stages. In the first phase, two carbons emanating from citrate react with oxygen to produce CO2. The end result is a four carbon compound known as succinyl- CoA. In the second phase, Succinyl- CoA is converted into oxaloacetate, and therefore, increasing the possibility of restarting the process. In every tricarboxylic cycle, two carbons are obtained from acetyl- CoA, and two carbons react with oxygen to generate carbon dioxide (Goodsell, 2012).

Application of the topic

The Tricarboxylic cycle is critical to life because of its amphibolic role. There is no citric acid cycle enzyme absence that has been reported. Citric acid cycle can be incorporated in the cardio- protection. For several decades, prior to the complete explanation of the citric acid cycle, hypoxia and ischemia were believed to stimulate the degradation of glutamate and myocardial aspartate, which led to the creation of succinate in secluded hearts. Thus, it has been suggested that the above- stated channeling can help in the production of ATP when there is deficiency of oxygen. Such examinations made researchers hope that the manipulation of the cycle can promote cardio- protection. More so, maintaining the generation of adequate cellular energy is essential for body functioning, and its disruption can lead to medical conditions (Czibik, Steeples, Yavari & Ashrafian, 2014).


Aerobic organisms utilize the citric acid cycle to generate energy.  The acetyl- CoA which is obtained from carbohydrates, proteins and fats is oxidized to generate ATP and carbon dioxide. The cycle was established in 1937 by Krebs Hans Adolf and William Arthur Johnson. The cycle is essential because it produces energy essential for body functioning and acts as a major pathway for the metabolism of proteins, carbohydrates and fat. The citric acid cycle acts as the powerhouse of energy. In this regard, it offers electrons, the fuel required in the process of oxidizing phosphoryl so as to generate ATP and energy. All these processes take place in the mitochondria. 


Chabra, N. (2017). Significance of TCA cycle. Retrieved from

Czibik, G., Steeples, V., Yavari, A., & Ashrafian , H. (2014, October 21). Citric acid

intermediates in cardio- protection. Retrieved from

Ward, C. (n.d.) The Tricarboxylic acid cycle. Diapedia. Retrieved from

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